Structural identification and synthesis of luciferin from the bioluminescent earthworm, Diplocardia longa

For the first time, luciferin from a bioluminescent earthworm has been purified, identified, and synthesized. This luciferin from the North American species, Diplocardia longa, is a simple aldehyde compound, N-isovaleryl-3-aminopropanal, with an amide functional group. It is a clear, odorless oil at room temperature. It is nonvolatile and has no near-uv-visible absorption or fluorescence. Derivatives of this compound were made to facilitate its identification: the luciferin 2,4-dinitrophenylhydrazone (mp 174 degrees C), a yellow crystalline solid; and the luciferin alcohol, a clear oil. Synthesis of Diplocardia luciferin yielded an oil of identical spectroscopic (proton nuclear magnetic resonance (NMR), 13C NMR, mass, and ir), chemical (dinitrophenylhydrazone and alcohol derivatives, bioluminescence activity), and physical (thin-layer chromatography, volatility) properties to those of the purified native Diplocardia luciferin.